Organic light-emitting devices attract much attention as self-emitting devices which are expected to be decreased in thickness and power consumption.
A display including an active matrix-type organic light-emitting device provided in a display portion and including a thin film transistor provided as a switching element in each pixel can realize high-definition, high-quality display and is thus used in a variety of fields. A drive circuit which controls the thin film transistor corresponding to each pixel is provided in a peripheral region around an emission region in which pixels are disposed, and, besides the drive circuit, wirings such as power supply wiring, signal wiring, and the like are formed in the peripheral region. A thin film transistor connected to each pixel and a drive circuit provided in the peripheral region are important factors which determine display quality.
An organic EL element which constitutes an organic light-emitting device includes a first electrode, a second electrode, and a plurality of organic compound layers having different functions, such as a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, which are laminated between both electrodes.
The organic EL element holds a problem that entering of moisture and gases into the element causes a decrease in luminance and an increase in drive voltage. In an organic light-emitting device, therefore, in order to prevent atmospheric moisture and gases from entering the organic compound layers of the organic El element, a sealing layer is disposed on the side of a substrate on which the organic EL element is provided, and the peripheries of the substrate and the sealing layer are sealed with a sealant.
Even if entering of atmospheric moisture and gases can be interrupted by the sealing layer and the sealant, when constituents which constitute an organic light-emitting device contain moisture and gases, diffusion of moisture and gases in the organic light-emitting device proceeds to degrade organic EL elements, thereby decreasing luminance.
In particular, in an active matrix-type organic light-emitting device, a planarization film including an organic photosensitive insulating film is provided to cover thin-film transistors and drive circuits. The planarization film is provided for planarization by decreasing steps produced by forming thin-film transistors and drive circuits, and organic EL elements are formed on the planarization film. Further, in some organic light-emitting devices, in order to separate elements from each other, an element separation film including an organic insulting film is formed on a planarization film. A resin film such as the organic insulating film which constitutes the planarization film or the element separation film is easily permeable to moisture and gases and easily adsorbs moisture and gases therein. Therefore, in such a type of organic light-emitting device, moisture and gases easily remain in the device, and the remaining moisture and gases diffuse in the resin layer and enter organic compound layers of organic EL elements, thereby causing deterioration of light emission.
In a display device disclosed in Japanese Patent Laid-Open No. 2006-054111, in order to solve the problem, a planarization film and an element separation film each composed of a resin are removed from a portion surrounding an emission region to form a separation groove which separates an inner peripheral portion from an outer peripheral portion. Therefore, moisture present in a portion of the planarization film and the element separation film, which corresponds to the outer peripheral portion, does not enter a portion of the planarization film and the element separation film, which corresponds to the inner peripheral portion, through the planarization film and the element separation film, thereby preventing deterioration of organic EL elements due to moisture in a display region.
In the configuration of Japanese Patent Laid-Open No. 2006-054111, the moisture and gases present in the planarization film and the element separation film corresponding to a periphery of the emission region can be suppressed from entering the planarization film and the element separation film within the emission region through the planarization film and the element separation film. However, the organic EL elements deteriorate due to the influence of the moisture and gases remaining the planarization film and the element separation film within the emission region, thereby causing difficulty in achieving long-term reliability required for an organic EL light-emitting device.
As a result of keen examination, the inventors of the present invention found that moisture and gases remaining in the planarization film and the element separation film disposed in a periphery of the emission region diffuse into a space (sealing space) between a substrate and a sealing layer, enter the planarization film and the element separation film within the emission region, and diffuse to organic compound layers in each pixel. Further, when sufficient sealing cannot be achieved due to damage to a sealant, atmospheric moisture and gases enter the space between the substrate and the sealing layer from the outside, are absorbed by the planarization film and the element separation film, and diffuse into organic EL elements, thereby causing deterioration of the organic EL elements.